Lung epithelial stem/progenitor cells are critical for maintenance of homeostasis of airway epithelial and alveolar epithelial cell populations;therefore they represent the key targets for exploring the pathogenesis of lung diseases and the repair mechanism of injury. The potential use of embryonic stem (ES) cell derived tissue stem/progenitor cells to generate disease models or to explore their therapeutic potential in regenerative medicine has fueled a tremendous amount of research activity to develop methods that promote the differentiation of ES cells into tissue specific stem/progenitor cells. There are at least three stem/progenitor cell types responsible for the maintenance of distal lung epithelial cells: 1) transient amplifying (TA) Clara cells;2) bronchiolar stem cells or bronchioalveolar stem cells and 3) alveolar epithelial type II (ATII) cells. Loss of normal functions of any of these stem/progenitor cell types due to injuries or genetic deficiencies is thought to play an important role in development of chronic or severe pulmonary diseases, including pulmonary fibrosis, asthma, CODP, cystic fibrosis and neonatal respiratory distress syndrome (RDS). The overall objective of this proposal is to develop procedures of genetic selections for isolation, purification and characterization of the above three types of distal lung stem/progenitor cells derived from mouse embryonic stem cells (mES), and to explore the therapeutic potential of these mES derived stem/progenitor cells in the treatment of lung injuries. The specific aims of this proposal are driven by the central hypothesis that a single genetically modified mES cell line harboring a dual protein marker-drug resistant fusion transgene controlled by Clara cell-specific promoter and ATII cell-specific promoter, respectively, can be selectively induced to differentiate into an essential pure population of either bronchiolar stem cells, Clara cells, or ATII cells. This will allow us to characterize these distal lung stem/progenitors'properties, in vitro and in vivo, and to explore their capacity in the regeneration and repair of injured lung using naphthalene induced- and bleomycin-induced lung injury models. PUBLIC HEALTH RELEVANCE: There are 35 million Americans with lung disease, and it is collectively the number 3 killer in the United States. Embryonic stem (ES) cells derived lung stem/progenitor cells provide a promising source of cells that could be used as model for study of pathogenesis of diseases and used therapeutically to treat lung injuries as well as pulmonary genetic disorders. This exploratory grant application proposes to isolate, purify, and characterize mouse ES cell derived distal lung stem/progenitor cells as well as to evaluate the therapeutic use of lung epithelial stem/progenitor cells derived from mouse ES cells in mouse models of lung injuries.